Human alpha 2-macroglobulin and the complement component proteins, C-3 and C-4 have in common the covalent reaction with methylamine. These proteins undergo an autolytic peptde fragmentation at the site of methylamine incorporation. We have sequenced the amino acid residues around this reactive in alpha 2M. We will extend our work to the two complement proteins. The second study in our laboratory will be the establishment of the amino acid sequences around the protease cleavage site in alpha 2M.